Efficient Degradation of Tetracycline by Peroxymonosulfate Activated with Ni-Co Bimetallic Oxide Derived from Bimetallic Oxalate

In this work, NiCo2O4 was synthesized from bimetallic oxalate and utilized as a heterogeneous catalyst to active peroxymonosulfate (PMS) for the degradation of tetracycline (TC). The degradation efficiency of TC (30 mg/L) in the NiCo2O4 + PMS system reached 92.4%, with NiCo2O4 exhibiting satisfactory reusability, stability, and applicability. Radical trapping test and electron paramagnetic resonance (EPR) results indicated that SO4•−, •OH, O2•−, and 1O2 were the dominating reactive oxygen species (ROS) for TC degradation in the NiCo2O4 + PMS system. Seven intermediates were identified, and their degradation pathways were proposed. Toxicity assessment using T.E.S.T software (its version is 5.1.1.0) revealed that the identified intermediates had lower toxicity compared to intact TC. A rice seed germination test further confirmed that the NiCo2O4 + PMS system effectively degraded TC into low-toxicity or non-toxic products. In conclusion, NiCo2O4 shows promise as a safe and efficient catalyst in advanced oxidation processes (AOPs) for the degradation of organic pollutants.